The aim of this research project is to evaluate a series of bridgehead nitrogen heterocycles of the purine type as anticancer agents. These systems will be synthesized using standard ring-closure procedures, utilizing heterocyclic N-ylides in cycloadditions, heteroaromatic betaines as a source of 1,3- and 1,4-dipoles, and by photochemical methods. Five, six and larger ring-fused systems will be included in the study.